Many conventional firearms are configured to be hand-held by a user. For example, many such firearms (e.g., long guns, or firearms with relatively long barrels) provide a first gripping portion in a forward position that is adjacent to or overlies the firearm's barrel and a second gripping portion in a rearward position adjacent the firearm's trigger. The first gripping portion of some conventional firearms comprises a hand guard adjoining the barrel. Such hand guards can be uncomfortable for users, for example, as the barrel temperature increases from repeatedly firing the firearm.
Other hand guards that do not physically touch the barrel have also been proposed. For example, U.S. Pat. No. 5,343,650 discloses an extended rigid frame receiver sleeve having protective spring-loaded hand guards.
Some conventional firearms comprise a receiver and a barrel removably coupled to the receiver. In some firearms, such as, for example, an AR-15 type semi-automatic rifle, a barrel nut couples the barrel to the receiver.
Referring to FIG. 1, a barrel nut and modular hand grip having an upper portion, a lower portion and a coupling assembly are shown, as disclosed in U.S. Pat. No. 7,216,451. A rearward end of the upper portion is configured to engage a top portion of the barrel nut. The coupling assembly is engagable with a bottom portion of the barrel nut and is attached to the rearward end of the upper portion. The upper portion defines spaced lug rails, and the lower portion defines a plurality of spaced lugs that are receivable in the gaps in the lug rails.
AR-15 type firearms comprise separate upper and lower receiver assemblies, which are typically coupled to each other using two through-pins. Such receivers can be quickly interchanged without the aid of tools. Many AR-15 type rifles are also highly configurable and customizable, and are commonly fitted with one or more detachable accessories. Such accessories include a bipod, a foldable or collapsable stock, a threaded barrel configured to attach a flash suppressor, and/or a rail system configured to removably attach still other accessories.
Early rail systems were originally configured to receive a telescopic sight (also referred to herein as a “scope”). Such rail systems became widely adopted, and their use expanded to include other accessories, such as tactical lights, night vision devices, laser sighting modules, reflex sights, fore grips, bipods, and bayonets. Today certain combinations of rails and accessories have even displaced the original sights (so-called “iron sights”) of many firearms. Rails have also been proposed for the undersides of frames and even on grips.
In some semi-automatic (and automatic versions) of firearms, and in particular AR-15 type firearms, direct gas impingement provides the necessary forces for re-cocking the firearm (i.e., repositioning the bolt and firing pin assembly to make the firearm ready to fire a second bullet subsequent to firing a first bullet). In such direct gas impingement configurations, expanding gas that pushes a fired bullet through the bore of the barrel flows through a gas port in a distal end of the barrel and into a gas tube typically positioned above and longitudinally aligned with the barrel, as shown in FIG. 2. Such a gas tube fluidically couples the gas port and a gas chamber (sometimes referred to as a “gas key” or bolt carrier key) in the upper receiver. A bolt and bolt carrier in the upper receiver together form a piston, which is driven in a rearward (i.e., toward the firearm's stock) direction by the pressure of such a flow of gas. Such rearward movement by the bolt carrier causes the spent cartridge to be extracted from the firing chamber and ejected through an ejection port in the upper receiver. The bolt and bolt carrier movement also chambers another, unfired, cartridge in the firing chamber and re-cocks the firearm.
Other conventional semiautomatic (and automatic) firearms are also well known. For example, the AK-47 and SIG-556 represent two popular firearms having many similar and derivative designs that are commercially available. As noted above, some conventional firearms have a gas-impingement system configured to chamber an unfired cartridge and re-cock the firearm. Other conventional firearms have a piston system, or other system, configured to chamber an unfired cartridge and re-cock the firearm. Such piston or other systems can have related components (e.g., different than a gas tube) extending longitudinally adjacent to the barrel.
Rapid succession firing can heat the firearm's barrel, making conventional hand guards unsuitable for use during extended periods of such firing. For example, conventional hand guards can increase in temperature and be uncomfortable for a user, and can also restrict airflow around the barrel. In addition, prior hand guards have been difficult to assemble.